Vibration damping means which are not attached between two portions but only to one vibrating portion of a device are referred to as a vibration absorber, or briefly as an absorber, or a pendulum-type absorber. Due to a stretchable or compressible connection between a mass of the absorber and the vibrating portion, the mass of the absorber follows the movements of the portion with a certain delay. Due to the stretching and/or compression, energy is withdrawn from the vibration movement, and in this way a damping effect is obtained.
Typically, the mass including the deformable connection, i.e. stretchable and/or compressible and/or twistable connection, has a natural frequency. The latter is usually set to a specific proportion of the vibration frequency to be damped. At this optimized frequency the mass will be deflected widely, so that correspondingly large forces and correspondingly large energies are transferred from the vibrating portion to the absorber mass.
From DE 197 25 770 A1 a device for damping vibrations is known which comprises a vibration absorber. The vibration absorber includes a mass resiliently coupled to the resilient system, the mass being coupled to the resilient system through a controllable actuator which is variable in length in the operating direction of the vibration absorber. This is intended to dampen vibrations in an enlarged frequency range as compared to a passive vibration damping system. Similar principles are also disclosed in DE 10 2006 056 757 A1 and DE 10 2010 002 262 A1, for damping vibrations of buildings.
The absorbers described in DE 6 941 4628 T2 and in EP 6 183 80 B1 are based on another mechanism of action. Here, the absorbers are attached to pendulum-like structures and virtually constitute a pendulum-type absorber. Specifically, a vibration absorber for cable car gondolas is provided, with a movable damping mass member attached to the pendulum structure of the gondola above the center of gravity thereof. EP 6 183 80 B1 furthermore gives an overview of industrial applications of absorbers which are likewise considered for the invention.
DE 10 2006 053 232 B4 discloses an absorber with two directions of action. This absorber is intended to damp a vibration of a conduit, for example, and may also be operated actively. The active absorber comprises at least two actuators acting in different movement directions, and a fastening device. The actuators are coupled to the fastening device via leaf springs. Additionally, the two actuators are coupled with each other by a connecting member.
DE 10 2010 039 977 A1 discloses a piston-shaped passive absorber which retains a balancing mass within a piston so as to be movable at a defined friction.